Bush, in remarks prepared for delivery to the US National Defense University and released by the White House late Monday, was to say all three countries "pose unique challenges for our country" in the worldwide conflict.

"They are all theaters in the same overall struggle. In all three places, extremists are using violence and terror in an attempt to impose their ideology on whole populations," Bush said in the advance text.

His message came amid media reports of multiple strikes inside Pakistan recently by US or international troops based in Afghanistan, which accuses its neighbour of abetting or at least turning a blind eye to cross-border violence.

"Defeating these terrorist and extremists is in Pakistan's interest because they pose a mortal threat to Pakistan's future as a free and democratic nation," Bush said in the prepared remarks.

"Defeating these terrorist and extremists is also Pakistan's responsibility because every nation has an obligation to govern its own territory and make certain that it does not become a safe haven for terror," he said.

Bush, who leaves office in late January, said the United States and NATO would help Pakistan battle extremists, and expressed sorrow for any loss of innocent life, amid complaints in Pakistan and Afghanistan of civilian deaths.